Emulsions have become more important in various industrial applications such as cosmetics, food products and drugs. However, the emulsions tend to have such a problem that an emulsified condition thereof becomes unstable with time. To solve this problem, various attempts have been conventionally made. As one of the conventional attempts, there is known the method in which a hydrophobic modified polysaccharide obtained by reacting a polysaccharide with a hydrophobic agent, etc., is compounded in the emulsions.
As to the hydrophobic modified polysaccharides, for example, Patent Document 1 discloses the method for producing a modified cellulose ether in which a water-soluble cellulose ether containing a hydroxyalkyl group is reacted with a glycidyl ether containing an alkyl group having 6 to 26 carbon atoms.
Also, Patent Document 2 discloses the method for producing a carboxymethyl alkyl cellulose in which a carboxymethyl cellulose metal salt is reacted with an alkyl halide.
Patent Document 3 discloses the method for producing a polyuronic acid salt in which a low-crystalline cellulose derivative having a crystallinity of 30% or less is subjected to oxidation reaction in the presence of an N-oxyl compound to selectively oxidize a primary hydroxyl group bonded at the C6-position of an anhydroglucose unit constituting a main chain of a cellulose.
Patent Document 4 discloses the method for producing a modified polyuronic acid salt in which a primary oxidant such as an N-oxyl compound and manganese acetate and a terminal oxidant such as peracetic acid are added to a cellulose ester mixture having a pH of less than 4 to convert the C6 hydroxyl group of an anhydroglucose unit of a cellulose to a formyl group or a carboxy group.    Patent Document 1: JP 3-12401A    Patent Document 2: JP 4-130101A    Patent Document 3: JP 2009-263641A    Patent Document 4: JP 2007-515515A